Process for preparing polycarbonate using sterically hindered secondary amine catalysts

ABSTRACT

An interfacial polymerization process for preparing high molecular weight aromatic polycarbonates by reacting a dihydric phenol with a carbonate precursor in the presence of a catalytic amount of certain sterically hindered secondary amines or their salts.

This invention is directed to an interfacial polymerization process forpreparing high molecular weight aromatic polycarbonates which comprisesreacting under interfacial polycarbonate-forming conditions a dihydricphenol and a carbonate precursor in the presence of a catalytic amountof a sterically hindered secondary amine or a salt thereof.

BACKGROUND OF THE INVENTION

Polycarbonates are well known thermoplastic materials finding a widerange of uses, particularly for injection molding applications and asglazing sheet for replacement of window glass. The interfacialpolymerization technique, which is one of the methods employed inpreparing a polycarbonate, involves reacting a dihydric phenol and acarbonate precursor in the presence of an aqueous caustic solutioncontaining an alkali or alkaline earth metal hydroxide, and an inertorganic solvent medium which is a solvent for the polycarbonate as it isformed. While the interfacial polymerization process is generallyeffective in producing polycarbonates, it does, in general, suffer fromtwo disadvantages. Firstly, the rate of reaction is relatively slow.Secondly, there is a general difficulty in producing high molecularweight aromatic polycarbonates, i.e., those having a weight averagemolecular weight of about 15,000 to greater. Many techniques, such asthose employing ultrasonic waves during the reaction, have been employedto remedy these two disadvantages. These techniques have not alwaysproved to be entirely effective and involve the use of cumbersome andexpensive equipment. It is advantageous economically to speed up thereaction and to produce high molecular weight aromatic polycarbonateswithout having to employ extra equipment or more severe reactionconditions. One such method is the use of catalysts in the interfacialpolymerization process.

However, there is generally relatively little known about effectivecatalysis of polycarbonate reactions. The prior art discloses thatcertain compounds such as tertiary and quaternary amines and their salts(U.S. Pat. No. 3,275,601), guanidine compounds (U.S. Pat. No.3,763,099), and ammonia and ammonium compounds (U.S. Pat. No. 4,055,544)are effective catalysts for the interfacial polymerization process forproducing polycarbonates. However, the prior art also teaches thatcertain organic nitrogen compounds function as molecular weightregulators or chain terminators in the polycarbonate reactions. Thus,the afore-mentioned U.S. Pat. No. 3,275,601 discloses that aniline andmethyl aniline function as chain terminators in the polycarbonatereaction, while U.S. Pat. No. 4,001,184 discloses that primary andsecondary amines are effective molecular weight regulators. Furthermore,U.S. Pat. No. 4,111,910 teaches that ammonia, ammonium compounds,primary amines, and secondary amines function as chain terminators inthe formation of polycarbonates via the interfacial polymerizationprocess, and U.S. Pat. No. 3,223,678 teaches that monoethanolamine andmorpholine act to break the polycarbonate chain thereby resulting inlower molecular weight polycarbonates.

DESCRIPTION OF THE INVENTION

This invention is directed to an interfacial polymerization process forproducing high molecular weight aromatic carbonate polymers wherein adihydric phenol is reacted with a carbonate precursor in the presence ofan aqueous caustic solution containing an alkali metal or alkaline earthmetal hydroxide and a catalyst which is a sterically hindered secondaryamine or a salt of a sterically hindered secondary amine.

The reaction of a dihydric phenol such as2,2-bis(4-hydroxyphenyl)propane with a carbonate precursor such asphosgene results in a high molecular weight aromatic polycarbonatepolymer consisting of dihydric phenol derived units bonded to oneanother through carbonate linkages. The reaction is carried out in thepresence of an aqueous caustic solution containing the alkali andalkaline earth metal hydroxide as acid acceptors and an inert organicsolvent medium which is a solvent for the polycarbonate as it is formed.Generally, a molecular weight regulator is also present to control themolecular weight of the polycarbonate polymer. In the process of thepresent invention, a sterically hindered secondary amine is present andacts as an effective catalyst to speed up the reaction between thecarbonate precursor and the dihydric phenol.

The high molecular weight aromatic carbonate polymers produced inaccordance with the practice of this invention include carbonatehomopolymers of dihydric phenols or carbonate copolymers of two or moredifferent dihydric phenols. Additionally, the production of highmolecular weight thermoplastic randomly branched polycarbonates andcopolyester-polycarbonates are included within the scope of thisinvention. The randomly branched polycarbonates are prepared bycoreacting a polyfunctional organic compound with the afore-describeddihydric phenol and carbonate precursor.

The dihydric phenols employed in the practice of this invention areknown dihydric phenols in which the sole reactive groups are the twophenolic hydroxyl groups. Some of these are represented by the generalformula ##STR1## wherein A is a divalent hydrocarbon radical containing1-5 carbon atoms, ##STR2## X is independently hydrogen, halogen, or amonovalent hydrocarbon radical such as an alkyl group of 1-4 carbons, anaryl group of 6-10 carbons such as phenyl, tolyl, xylyl, naphthyl, anoxyalkyl group of 1-4 carbons or an oxyaryl group of 6-10 carbons and nis 0 or 1.

Typical of some of the dihydric phenols that can be employed in thepractice of the present invention are bisphenols such asbis(4-hydroxyphenyl)methane, 2,2-bis(4-hydroxyphenyl)propane (also knownas bisphenol-A), 2,2-bis(4-hydroxy-3-methylphenyl) propane,4,4-bis(4-hydroxyphenyl)heptane,2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane,2,2-bis(4-hydroxy-3,5-dibromophenyl) propane, etc., dihydric phenolethers such as bis(4-hydroxyphenyl) ether,bis(3,5-dichloro-4-hydroxyphenyl)ether, etc.; dihydroxydiphenyls such asp,p'-dihydroxydiphenyl, 3,3'-dichloro-4,4'-dihydroxydiphenyl, etc.;dihydroxyaryl sulfones such as bis(4-hydroxyphenyl)sulfone,bis(3,5-dimethyl-4-hydroxyphenyl)sulfone, etc., dihydroxy benzenes,resorcinol, hydroquinone, halo- and alkyl-substituted dihydroxy benzenessuch as 1,4-dihydroxy-2,5-dichlorobenzene,1,4-dihydroxy-3-methylbenzene, etc., and dihydroxy diphenyl sulfides andsulfoxides such as bis(4-hydroxyphenyl)sulfide andbis(4-hydroxyphenyl)sulfoxide,bis-(3,5-dibromo-4-hydroxyphenyl)sulfoxide, etc. A variety of additionaldihydric phenols are also available and are disclosed in U.S. Pat. Nos.2,999,835; 3,028,365 and 3,153,008, all of which are incorporated hereinby reference. It is, of course, possible to employ two or more differentdihydric phenols or a copolymer of a dihydric phenol with glycol or withhydroxy or acid terminated polyester, or with a dibasic acid in theevent a polycarbonate copolymer or interpolymer rather than ahomopolymer is desired for use in the preparation of the polycarbonatepolymers of this invention. Also employed in the practice of thisinvention are blends of any of the above dihydric phenols, the preferreddihydric phenol is bisphenol-A. The polyfunctional organic compoundswhich may be included within the scope of this invention are set forthin U.S. Pat. Nos. 3,635,895 and 4,001,184, which are incorporated hereinby reference. These polyfunctional aromatic compounds contain at leastthree functional groups which are carboxyl, carboxylic anhydride,haloformyl, or mixtures thereof. Examples of these polyfunctionalaromatic compounds include trimellitic anhydride, trimellitic acid,trimellityl trichloride, 4-chloroformyl phthalic anhydride, pyromelliticacid, pyromellitic dianhydride, mellitic acid, mellitic anhydride,trimesic acid, benzophenonetetracarboxylic acid,benzophenonetetracarboxylic anhydride, and the like. The preferredpolyfunctional aromatic compounds are trimellitic anhydride ortrimellitic acid or their haloformyl derivatives. Also included hereinare blends of a linear polycarbonate and a branched polycarbonate.

The carbonate precursor can be either a carbonyl halide or abishaloformate. The carbonyl halides include carbonyl bromide, carbonylchloride, and mixtures thereof. The bishaloformates suitable for useinclude the bishaloformates of dihydric phenols such asbischloroformates of 2,2-bis(4-hydroxyphenyl)propane,2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane, hydroquinone, and thelike, or bishaloformates of glycols such as bishaloformates of ethyleneglycol, and the like. While all of the above carbonate precursors areuseful, carbonyl chloride, also known as phosgene, is preferred.

By adding monofunctional compounds which are capable of reacting withphosgene or with the end groups of the polycarbonates consisting of thechlorocarbonic acid ester group and which terminate the chains, such asthe phenols, e.g., phenol, tert-butylphenyl, cyclohexylphenol, and2,2-(4,4-hydroxyphenylene-4'-methoxyphenylene)propane, aniline andmethylaniline, it is possible to regulate the molecular weight of thepolycarbonates.

As mentioned hereinabove, the acid acceptor is an alkali or alkalineearth metal hydroxide. Illustrative of these acid acceptors are sodiumhydroxide, lithium hydroxide, potassium hydroxide, calcium hydroxide andthe like. The amount of said acid acceptor present should be sufficientto maintain the pH of the aqueous caustic solution above about 9.

Illustrative of the inert organic solvents which are present during thereaction and which dissolve the polycarbonate as it is formed arearomatic hydrocarbons and halogenated hydrocarbons such as benzene,toluene, xylene, chlorobenzene, orthodichlorobenzene, chloroform,methylene chloride, carbon tetrachloride, trichloroethylene anddichloroethane. The solvent is present in an amount effective tosolubilize or dissolve substantially all of the polycarbonate as it isformed.

The catalytic compounds within the scope of the instant invention arecertain open-chain sterically hindered secondary amines and their salts.The open-chain secondary amines are represented by the general formula##STR3## wherein R¹ and R are individual substituent groups which arenot chemically joined together. In Formula I, R is a sterically bulkygroup while R¹ may or may not be a sterically bulky group. In apreferred embodiment, both R and R¹ are sterically bulky groups. InFormula I, R is selected from C₅ to C₃₀ linear alkyl radicals,substituted C₅ to C₃₀ linear alkyl radicals, C₃ to C₃₀ branched alkylradicals, C₃ to C₃₀ substituted branched alkyl radicals, C₅ to C₃₀linear alkenyl radicals, substituted C₅ to C₃₀ linear alkenyl radicals,C₃ to C₃₀ branched alkenyl radicals, substituted C₃ to C₃₀ branchedalkenyl radicals, C₃ to C₁₂ cycloaliphatic radicals, substituted C₃ toC₁₂ cycloaliphatic radicals, heterocyclic ring radicals containing from3 to 12 ring carbon atoms and one atom selected from the groupconsisting of oxygen and sulfur, substituted heterocyclic ring radicalscontaining 3 to 12 ring carbon atoms and one atom selected from oxygenand sulfur, C₇ to C₂₀ aralkyl radicals, and substituted C₇ to C₂₀aralkyl radicals; and R¹ is selected from C₁ to C₃₀ alkyl radicals,substituted C₁ to C₃₀ alkyl radicals, C₂ to C₃₀ alkenyl radicals,substituted C₂ to C₃₀ alkenyl radicals, C₃ to C₁₂ cycloaliphaticradicals, substituted C₃ to C₁₂ cycloaliphatic radicals, heterocyclicring radicals containing from 3 to 12 ring carbon atoms and one atomselected from the group consisting of oxygen and sulfur, substitutedheterocyclic ring radicals containing from 3 to 12 ring carbon atoms andone atom selected from the group consisting of oxygen and sulfur, C₇ toC₂₀ aralkyl radicals, and substituted C₇ to C₂₀ aralkyl radicals.

Preferably R¹ is selected from C₅ to C₃₀ linear alkyl radicals,substituted C₅ to C₃₀ linear alkyl radicals, C₃ to C₃₀ branched alkylradicals, substituted C₃ to C₃₀ branched alkyl radicals, C₅ to C₃₀linear alkenyl radicals, substituted C₅ to C₃₀ linear alkenyl radicals,C₃ to C₃₀ branched alkenyl radicals, substituted C₃ to C₃₀ branchedalkenyl radicals, C₃ to C₁₂ cycloaliphatic radicals, substituted C₃ toC₁₂ cycloaliphatic radicals, heterocyclic ring radicals containing from3 to 12 ring carbon atoms and one atom selected from the groupconsisting of oxygen and sulfur, substituted heterocyclic ring radicalscontaining from 3 to 12 ring carbon atoms and one atom selected from thegroup consisting of oxygen and sulfur, substituted heterocyclic ringradicals containing from 3 to 12 ring carbon atoms and one atom selectedfrom the group consisting of oxygen and sulfur, C₇ to C₂₀ aralkylradicals, and substituted C₇ to C₂₀ aralkyl radicals.

If R and R¹ represents C₃ to C₁₂ cycloaliphatic or substituted C₃ to C₁₂cycloaliphatic radicals, these cycloaliphatic or substitutedcycloaliphatic radicals are preferably C₃ to C₁₂ cycloalkyl orsubstituted C₃ to C₁₂ cycloalkyl radicals.

When substituent groups are present, these substituent groups arepreferably selected from hydroxyl, alkyl and alkoxy radicals.

Representative examples of the C₅ to C₃₀ linear alkyls include n-pentyl,n-hexyl, n-octyl, n-decyl, n-dodecyl, n-octadecyl and n-docosanyl.

Representative examples of the C₃ to C₃₀ branched alkyl radicals includeisopropyl, isobutyl, sec-butyl, tertiary butyl, tertiary-pentyl,2-ethylhexyl, neopentyl and 1 -methyl-undecylenyl.

Representative examples of the C₃ to C₁₂ cycloaliphatic radicals includecyclohexyl, cyclopentyl, cyclobutyl and cyclododecyl. Preferred C₃ toC₁₂ cycloaliphatic and substituted C₃ to C₁₂ cyclolaiphatic radicals arethe C₃ to C₁₂ cycloalkyl and C₃ to C₁₂ substituted cycloalkyl radicals.

Representative examples of the heterocyclic ring containing from 3 to 12ring carbon atoms and one atom selected from the group consisting ofoxygen and sulfur include tetrahydrofurfuryl and tetrahydrothenyl.

Representative examples of the C₇ to C₂₀ aralkyl radicals includebenzyl, 2-phenylethyl, 2-phenyl-1-propyl, cumyl, 3-phenyl-1-propyl and1-naphthylmethyl.

Representative examples of the C₂ to C₃₀ alkenyl radicals include vinyl,allyl, propenyl, 2-butenyl, 2-methylpropenyl, 3-octenyl, and the like.

Preferred compounds of Formula I are those wherein R and R¹ bothrepresent sterically bulky groups, i.e., wherein R and R¹ areindependently selected from C₅ to C₃₀ linear alkyl radicals, C₅ to C₃₀substituted linear alkyl radicals, C₃ to C₃₀ branched alkyl radicals,substituted C₃ to C₃₀ branched alkyl radicals, linear C₅ to C₃₀ alkenylradicals, substituted linear C₅ to C₃₀ alkenyl radicals, branched C₃ toC₃₀ alkenyl radicals, branched C₃ to C₃₀ alkenyl radicals, substitutedbranched C₃ to C₃₀ alkenyl radicals, C₃ to C₁₂ cycloaliphatic radicals,substituted C₃ to C₁₂ cycloaliphatic radicals, a heterocyclic ringcontaining from 3 to 12 ring carbon atoms and one atom selected from thegroup consisting of oxygen and sulfur, and a substituted heterocyclicring containing from 3 to 12 ring carbon atoms and one atom selectedfrom the group consisting of oxygen and sulfur.

Illustrative preferred compounds represented by Formula I are set forthin Table I.

                                      TABLE I                                     __________________________________________________________________________    (CH.sub.3).sub.3 CNHC(CH.sub.3).sub.3                                                            (n-C.sub.8 H.sub.17)NH(n-C.sub.8 H.sub.17)                  CH.sub.3 (CH.sub.2).sub.9 CH(CH.sub.3)NH(n-C.sub.4 H.sub.9)                                      ##STR4##                                                   ##STR5##                                                                                         ##STR6##                                                   ##STR7##                                                                                         ##STR8##                                                   ##STR9##                                                                                         ##STR10##                                                 __________________________________________________________________________

The salts of the sterically hindered secondary amines are represented bythe general formula ##STR11## wherein R and R¹ are as defined above; andY is an m valent anion, preferably one selected from the groupconsisting of a halide, sulfate, fulfite, phosphate, phosphite,carbonate, nitrate, nitrite and carboxylate.

The amount of the catalyst present during the reaction is a catalyticamount. By catalytic amount is meant an amount effective to catalyze thereaction between the dihydric phenol and the carbonate precursor toproduce the polycarbonate. Generally, this amount ranges from about 0.01to about 10 weight percent based on the weight of the dihydric phenolpresent.

The present process is carried out by reacting the dihydric phenol, suchas bisphenol-A, with a carbonate precursor, such as phosgene, in areaction medium consisting of an aqueous caustic solution and an inertorganic solvent for the polycarbonate and in the presence of a catalyticamount of the sterically hindered secondary amine or sterically hinderedsecondary amine salt catalyst.

The temperature at which this reaction proceeds may vary from below 0°C. to about 100° C. The reaction proceeds satisfactorily at temperaturesranging from about room temperature (25° C.) to about 50° C. Since thereaction is exothermic, the rate of carbonate precursor addition may beused to control the reaction temperature. The amount of carbonateprecursor, such as phosgene, required will generally depend upon theamount of dihydric phenol present. Generally, one mole of the carbonateprecursor will react with one mole of dihydric phenol to provide thepolycarbonate. When a carbonyl halide, such as phosgene, is used as thecarbonate precursor, two moles of hydrohalic acid such as HCl areproduced by the above reaction. These two moles of acid are"neutralized" by the alkali and alkaline earth metal hydroxide acidacceptor present. The foregoing are herein referred to as stoichiometricor theoretical amounts.

PREFERRED EMBODIMENT OF THE INVENTION

In order to more fully and clearly illustrate the present invention, thefollowing examples are presented. It is intended that the examples beconsidered as illustrative rather than limiting the invention disclosedand claimed herein. In the examples, all parts and percentages are on aweight basis unless otherwise specified.

EXAMPLE 1

This example illustrates an unsuccessful attempt to prepare apolycarbonate polymer via the interfacial polymerization techniquewithout the presence of a catalyst. To a reactor fitted with a refluxcondenser and a mechanical agitator, charge 57 parts of2,2-bis(4-hydroxyphenyl)propane, 157 parts of water, 325 parts ofmethylene chloride, and 1.2 parts of para-tertiary-butylphenol. Phosgeneis then added to the reaction mixture at a rate of 0.65 parts per minutefor a period of 30 minutes while maintaining the pH at 9 by the additionof a 15% aqueous sodium hydroxide solution. After 30 minutes, the pH israised to 11.0 by the use of additional amounts of sodium hydroxidesolution. Phosgenation is continued for a further 10 minutes at this pH.The material is recovered from the reaction and found to have anintrinsic viscosity of 0.12 dl./g. This indicates that no practicaldegree of polymerization is achieved.

EXAMPLE 2

To a reactor filled with a reflux condenser and a mechanical agitator,charge 75.2 grams of 2,2-bis(4-hydroxyphenyl)propane, 300 ml ofmethylene chloride, 200 ml of water and 1 gram oftert-butylcyclohexylamine. Phosgene is then added to the reactionmixture at the rate of 0.9 grams per minute for a period of 30 minuteswhile maintaining the pH at 9 by the addition of a 25% aqueous solutionof sodium hydroxide. After the 30 minute period, the pH is raised to11.0 by the use of additional amounts of sodium hydroxide solution.Phosgenation is continued for an additional 10 minutes at this pH,followed for an additional 7 minutes at pH 13.

The polycarbonate is recovered from solution, dried and is found to havean intrinsic viscosity of 0.48 dl./g. and a hydroxyl content of 0.018weight precent based on the weight of the polymer. This indicates thatthe formation of a high molecular weight polycarbonate polymer hasoccurred.

EXAMPLE 3

The procedure of Example 2 is substantially repeated, except that 0.65grams of diisopropylamine is substituted for thetert-butylcyclohexylamine. The polycarbonate is recovered from solutionand is found to have an intrinsiv viscosity of 0.36 dl./g. Thisindicates that formation of a high molecular weight polycarbonate hasoccurred.

EXAMPLE 4

The procedure of Example 2 is substantially repeated, except that 1.2grams of dicyclohexylamine is substituted for thetert-butylcyclohexylamine. The polycarbonate is recovered from solutionand is found to have an intrinsic viscosity of 0.22 dl./g. Thisindicates that formation of a high molecular weight polycarbonate hasoccurred.

EXAMPLE 5

The procedure of Example 2 is substantially repeated, except that 1.0grams of diisobutylamine is substituted for thetert-butylcyclohexylamine. The polycarbonate is recovered from solutionand is found to have an intrinsic viscosity of 0.32 dl./g. Thisindicates that formation of a high molecular weight polycarbonate hasoccurred.

EXAMPLE 6

The procedure of Example 2 is substantially repeated, except that 1.55grams of dioctylamine is substituted for the tert-butylcyclohexylamine.The polycarbonate is recovered from solution and is found to have anintrinsic viscosity of 0.41 dl./g. This indicates that formation of ahigh molecular weight polycarbonate has occurred.

EXAMPLE 7

The procedure of Example 2 is substantially repeated, except that 1.0grams of isopropylcyclohexylamine is substituted for thetert-butylcyclohexylamine. The polycarbonate is recovered from solutionand is found to have an intrinsic viscosity of 0.34 dl./g. Thisindicates that formation of a high molecular weight polycarbonate hasoccurred.

EXAMPLE 8

The procedure of Example 2 is substantially repeated, except that 1.4grams of dicyclooctylamine is substituted for thetert-butylcyclohexylamine. The polycarbonate is recovered from solutionand is found to have an intrinsic viscosity of 0.44 dl./g. Thisindicates formation of a high molecular weight polycarbonate.

EXAMPLE 9

This example illustrates the fact that when the secondary amines are notsterically hindered, i.e., fall outside the scope of Formula I, they donot function as effective catalysts.

The procedure of Example 2 is repeated, except that 1.0 grams of a 40%aqueous solution of dimethylamine is substituted for thetert-butylcyclohexylamine. The product is recovered from solution and isfound to have an intrinsic viscosity of 0.147 dl./g. This indicates thatno practical degree of polymerization is achieved.

EXAMPLE 10

This example further illustrates the fact that when non-stericallyhindered secondary amines, i.e., those secondary amines falling outsidethe scope of Formula I, are used, they are ineffective as catalysts.

The procedure of Example 2 is repeated, except that 0.55 grams ofdiethylamine is substituted for the tert-butylcyclohexylamine. Theproduct is recovered from solution and is found to have an intrinsicviscosity of 0.147 dl./g. This indicates that no practical degree ofpolymerization is achieved.

As can be seen by comparison of Example 1 with Examples 2-8, the use ofthe catalysts of the instant invention results in the production of highmolecular weight aromatic polycarbonates via the interfacialpolymerization techniques, while in the absence of a catalyst theinterfacial polymerization technique is ineffective in producing a highmolecular weight aromatic polycarbonate. Examples 9-10 clearly show thata non-sterically hindered secondary amine is ineffective as a catalyst,i.e., a secondary amine falling outside the scope of Formula I, in theinterfacial polymerization technique.

These Examples clearly indicate that the specific, sterically hinderedseconary amines or their salts as defined by Formulae I and II areeffective as catalysts in the interfacial polymerization reaction forproducing high molecular weight aromatic polycarbonates.

It will thus be seen that the objects set forth above, among those madeapparent from the preceding description, are efficiently attained, andsince certain changes may be made in carrying out the above process andthe composition set forth without departing from the scope of theinvention, it is intended that all matters contained in the abovedescription shall be interpreted as illustrative and not in a limitingsense.

What I claim is:
 1. An interfacial polymerization process for preparinga high molecular weight aromatic polycarbonate which comprises reacting,under interfacial polycarbonate-forming conditions, a dihydric phenolwith a carbonate precursor in the presence of a catalytic amount of asterically hindered secondary amine, or its acid addition salt, of theformula ##STR12## wherein R is selected from the group consisting of C₅to C₃₀ linear alkyl radicals, substituted C₃ to C₃₀ linear alkylradicals, C₃ to C₃₀ branched alkyl radicals, substituted C₃ to C₃₀branched alkyl radicals, C₅ to C₃₀ linear alkenyl radicals, substitutedC₅ to C₃₀ linear alkenyl radicals, C₃ to C₃₀ branched alkenyl radicals,substituted C₃ to C₃₀ branched alkenyl radicals, C₃ to C₁₂cycloaliphatic radicals, substituted C₃ to C₁₂ cycloaliphatic radicals,heterocyclic ring radicals containing 3 to 12 ring carbon atoms and oneatom selected from the group consisting of oxygen and sulfur,substituted heterocyclic ring radicals containing 3 to 12 ring carbonatoms and one atom selected from the group consisting of oxygen andsulfur, C₇ to C₂₀ aralkyl radicals, and substituted C₇ to C₂₀ aralkylradicals; and R¹ is selected from the group consisting of C₁ to C₃₀alkyl radicals, substituted C₁ to C₃₀ alkyl radicals, C₃ to C₁₂cycloaliphatic radicals, substituted C₃ to C₁₂ cycloaliphatic radicals,C₂ to C₃₀ alkenyl radicals, substituted C₂ to C₃₀ alkenyl radicals,heterocyclic ring radicals containing 3 to 12 ring carbon atoms and oneatom selected from the group consisting of oxygen and sulfur,substituted heterocyclic ring radicals containing 3 to 12 ring carbonatoms and one atom selected from the group consisting of oxygen andsulfur, C₇ to C₂₀ aralkyl radicals, and substituted C₇ to C₂₀ aralkylradicals.
 2. The process of claim 1 wherein the catalyst is a stericallyhindered secondary amine.
 3. The process of claim 2 wherein R¹ isselected from the group consisting of C₅ to C₃₀ linear alkyl radicals,substituted C₅ to C₃₀ linear alkyl radicals, C₃ to C₃₀ branched alkylradicals, substituted C₃ to C₃₀ branched alkyl radicals, C₅ to C₃₀linear alkenyl radicals, substituted C₅ to C₃₀ linear alkenyl radicals,C₃ to C₃₀ branched alkenyl radicals, substituted C₃ to C₃₀ branchedalkenyl radicals, C₃ to C₁₂ cycloaliphatic radicals, substituted C₃ toC₁₂ cycloaliphatic radicals, heterocyclic ring radicals containing 3 to12 ring carbon atoms and one atom selected from the group consisting ofoxygen and sulfur, substituted heterocyclic ring radicals containing 3to 12 ring carbon atoms and one atom selected from the group consistingof oxygen and sulfur, C₇ to C₂₀ aralkyl radicals, and substituted C₇ toC₂₀ aralkyl radicals.
 4. The process of claim 1 wherein the catalyst isan acid addition salt of a sterically hindered secondary amine.
 5. Theprocess of claim 4 wherein R¹ is selected from the group consisting ofC₅ to C₃₀ linear alkyl radicals, substituted C₅ to C₃₀ linear alkylradicals, C₃ to C₃₀ branched alkyl radicals, substituted C₃ to C₃₀branched alkyl radicals, C₅ to C₃₀ linear alkenyl radicals, substitutedC₅ to C₃₀ linear alkenyl radicals, C₃ to C₃₀ branched alkenyl radicals,substituted C₃ to C₃₀ branched alkenyl radicals, C₃ to C₁₂cycloaliphatic radicals, substituted C₃ to C₁₂ cycloaliphatic radicals,heterocyclic ring radicals containing 3 to 12 carbon atoms and one atomselected from the group consisting of oxygen and sulfur, substitutedheterocyclic ring radicals containing 3 to 12 ring carbon atoms and oneatom selected from the group consisting of oxygen and sulfur, C₇ to C₂₀aralkyl radicals, and substituted C₇ to C₂₀ aralkyl radicals.
 6. Theprocess of claim 2 wherein said dihydric phenol is bisphenol-A and saidcarbonate precursor is phosgene.
 7. The process of claim 6 wherein saidsterically hindered secondary amine catalyst is present in from about0.01 to about 10 weight percent based on the weight of said bisphenol-A.8. The process of claim 4 wherein said dihydric phenol is bisphenol-Aand said carbonate precursor is phosgene.
 9. The process of claim 8wherein said salt of a sterically hindered secondary amine catalyst ispresent in from about 0.01 to about 10 weight percent based on theweight of said bisphenol-A.